The invention relates to pressure indicating and monitoring gages of the type disclosed in U.S. Pat. No. 3,678,758, and the objective of the invention is to improve on and enlarge the monitoring capabilities of gages of that class.
More particularly, the invention embodies a Bourdon tube pressure gage with rotary sweep indicator pointer and a mechanical drive mechanism for the pointer as disclosed in the above-mentioned prior patent. A manually adjustable high pressure limit stop for the pointer is provided on the gage in accordance with the teachings of the prior art, and the Bourdon tube of the gage has a connection with external pressure to be monitored, such as the operating pressure of a pump, compressor or engine. A booster valve attached to the casing of the pressure gage receives full system control pressure through a high pressure input port. A low pressure input port of the booster valve receives reduced pressure through a regulator intervened between the booster valve and system supply. The booster valve has a full system pressure vent port normally closed by a differential area piston whose larger side is in communication with the low pressure chamber of the booster valve.
The low pressure chamber of the booster valve communicates through tubing inside of the pressure gage with a bleeder valve mounted on a carrier link attached to the movable extremity of the Bourdon tube and traveling therewith. The carrier link has the bleeder valve bodily mounted thereon to move therewith and the link has a lost motion connection with a pivoted arm forming a part of the sweep pointer drive mechanism of the gage. An actuator pin of the bleeder valve moves into contact with an abutment element on said pivoted arm to cause opening and venting of the bleeder valve chamber, thereby further reducing the pressure in the low pressure chamber of the booster valve and enabling the booster valve to vent full system pressure to atmosphere. This venting can effect the shutting down of a pump, compressor or engine quickly and automatically when such machine develops a dangerously high pressure.
In the above manner, the invention performs the functions of at least two separate devices commonly employed in the prior art and achieves the same results by a single integrated and simplified means. In the prior art, usually a panel mounted pressure or temperature indicating gage is employed in conjunction with a separate pressure or temperature sensing device equipped with a factory set trip point. By eliminating one of the two prior art devices, considerable economies are effected along with increased efficiency and convenience. It should be understood that the invention is applicable to either pressure or temperature monitoring Bourdon tube gages.
The beneficial features and advantages of the invention will become apparent to those skilled in the art during the course of the following description.